Method of Forming Metal Oxide and Apparatus for Performing the Same

ABSTRACT

In a method and an apparatus for forming metal oxide on a substrate, a source gas including metal precursor flows along a surface of the substrate to form a metal precursor layer on the substrate. An oxidizing gas including ozone flows along a surface of the metal precursor layer to oxidize the metal precursor layer so that the metal oxide is formed on the substrate. A radio frequency power is applied to the oxidizing gas flowing along the surface of the metal precursor layer to accelerate a reaction between the metal precursor layer and the oxidizing gas. Acceleration of the oxidation reaction may improve electrical characteristics and uniformity of the metal oxide.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.11/775,111, filed on Jul. 9, 2007, which in turn claims priority under35 USC §119 from Korean Patent Application No. 2006-64250, filed on Jul.10, 2006, the contents of both of which are herein incorporated byreference in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present disclosure is directed to a method of forming metal oxideand an apparatus for performing the same. More particularly, the presentdisclosure is directed to a method of forming metal oxide on asemiconductor substrate such as a silicon wafer using a plasma-enhancedatomic layer deposition (PEALD) and an apparatus for performing themethod.

2. Description of the Related Art

Semiconductor memory devices have been more highly integrated andoperated at higher speeds by significantly reducing the size of memorycells in the devices. A reduced memory cell size has correspondinglydecreased the area available for forming transistors and capacitors.Accordingly, lengths of transistor gate electrodes have been decreased.

Decreased length of the transistor gate electrode causes a correspondingdecrease in a thickness of a gate insulating layer beneath the gateelectrode. When the gate insulating layer is formed from silicon oxide(SiO₂) and has a thickness of less than about 20 Å, the operation of thetransistor may be degraded by an increase in leakage current due toelectron tunneling, infiltration of impurities in the gate electrode,and/or decrease in threshold voltage.

Capacitor capacitance in the memory cell decreases as the memory celldecreases in size. Reduction of the cell capacitance may cause theoperation of the memory cell to be degraded by deterioration of datareadability in the memory cell and/or increase in a soft error rate. Asa result, the memory device may not properly operate at a relatively lowvoltage due to the reduction in the cell capacitance.

To improve the cell capacitance of the semiconductor memory devicehaving a small cell region, it is known to form a dielectric layerhaving a very thin thickness. It is also known to form a lower electrodehaving a cylindrical shape or a fin shape so as to increase an effectivearea of the capacitors. In a dynamic random access memory (DRAM) devicehaving a storage capacity of more than about 1 gigabyte, however, theabove-mentioned approaches cannot be employed for manufacturing the DRAMdevice because these approaches do not enable a sufficiently high cellcapacitance for the DRAM device to be obtained.

To address the above-mentioned challenges, it is known to form adielectric layer using metal oxide having a high dielectric constantthat is greater than that of silicon nitride. The metal oxide may beformed by an atomic layer deposition (ALD), a PEALD, and the like.

Particularly, metal oxide may be formed on a semiconductor substrate bya lateral flow type PEALD process. The metal oxide formed by the lateralflow type PEALD process may have improved electrical characteristics ingeneral.

However, in the case where cylindrical lower electrodes having a highaspect ratio are formed on a semiconductor substrate and a metal oxidelayer is then formed on the cylindrical lower electrodes by the lateralflow type PEALD process, the metal oxide layer may have poorerelectrical characteristics in comparison with a metal oxide layer formedby a conventional ALD process.

SUMMARY OF THE INVENTION

Exemplary embodiments of the present invention provide methods offorming metal oxide having improved electrical characteristics.

Exemplary embodiments of the present invention also provide apparatusesfor forming metal oxide having improved electrical characteristics.

In accordance with an aspect of the present invention, a source gasincluding metal precursor may be supplied onto a substrate to allow thesource gas to flow along a surface of the substrate so that a metalprecursor layer is formed on the substrate. An oxidizing gas includingozone may be supplied onto the metal precursor layer to allow theoxidizing gas to flow along a surface of the metal precursor layer sothat the metal precursor layer may be oxidized. Metal oxide may beformed on the substrate. A radio frequency (RF) power may be applied tothe oxidizing gas flowing along the surface of the metal precursorlayer, so that an oxidation reaction between the metal precursor layerand the oxidizing gas may be accelerated.

In some exemplary embodiments of the present invention, examples ofmetal that may be used for the metal precursor may include zirconium(Zr), hafnium (Hf), aluminum (Al), tantalum (Ta), titanium (Ti),lanthanum (La), strontium (Sr), barium (Ba), praseodymium (Pr), lead(Pb), etc. These can be used alone or in a combination thereof.

In some exemplary embodiments of the present invention, a concentrationof the ozone in the oxidizing gas may be in a range of about 100 g/m³ toabout 1000 g/m³. Particularly, a concentration of the ozone in theoxidizing gas may be in a range of about 100 g/m³ to about 500 g/m³. Forexample, a concentration of the ozone in the oxidizing gas may be about200 g/m³.

In some exemplary embodiments of the present invention, the supply ofthe oxidizing gas and the application of the RF power may be performedsubstantially simultaneously.

In some exemplary embodiments of the present invention, an oxygen gasmay be supplied onto the substrate before supplying the oxidizing gas.The oxygen gas may be supplied for about 0.1 to about 3 seconds.

In some exemplary embodiments of the present invention, an interior of aprocess chamber in which the substrate is placed may be purged by apurge gas after forming the metal precursor layer, and the interior ofthe process chamber may be purged by a purge gas after forming the metaloxide.

In some exemplary embodiments of the present invention, the source gasand the oxidizing gas may flow from a first edge portion of thesubstrate towards a second edge portion opposite to the first edgeportion of the substrate.

In some exemplary embodiments of the present invention, the interior ofthe process chamber may be maintained at a pressure in a range of about0.1 to about 10 Torr, and the substrate may be maintained at atemperature in a range of room temperature to about 450° C.

In some exemplary embodiments of the present invention, after formingthe metal oxide, the substrate may be rotated by a predetermined angle,and then the supply of the source gas and the oxidizing gas, and theapplication of the RF power may be repeatedly performed.

In some exemplary embodiments of the present invention, the substratemay be continuously rotated, and the supply of the source gas and theoxidizing gas, and the application of the RF power may be repeatedlyperformed while rotating the substrate.

In accordance with another aspect of the present invention, an apparatusfor forming metal oxide may include a substrate stage, a chamber and aRF power source. The substrate stage may have a support region forsupporting a substrate and a peripheral region surrounding the supportregion. The chamber may be disposed on the peripheral region of thestage to define a space in which the substrate is placed. The space maybe defined by the support region of the stage and inner surfaces of thechamber. The chamber may have a gas inlet port for supplying a sourcegas including metal precursor to allow the source gas to flow along asurface of the substrate so that a metal precursor layer is formed onthe substrate. The gas inlet port may also supply an oxidizing gasincluding ozone to allow the oxidizing gas to flow along a surface ofthe metal precursor layer so that the metal precursor layer is oxidized.The metal oxide may be formed on the substrate by oxidizing the metalprecursor layer. The RF power source may be connected to the chamber forapplying a RF power to the oxidizing gas flowing along the surface ofthe metal precursor layer so that an oxidation reaction between themetal precursor layer and the oxidizing gas may be accelerated.

In some exemplary embodiments of the present invention, the apparatusmay further include a first gas supply section connected to the chamberfor supplying the source gas onto the substrate and a second gas supplysection connected to the chamber for supplying the oxidizing gas ontothe metal precursor layer. Example of the second gas supply section mayinclude an ozone generator.

In some exemplary embodiments of the present invention, the apparatusmay further include a third gas supply section for supplying a purge gasonto the metal precursor layer and the metal oxide, and a fourth gassupply section for supplying an oxygen gas onto the metal precursorlayer before supplying the oxidizing gas.

In some exemplary embodiments of the present invention, the chamber mayinclude a cover disposed on the peripheral region of the stage and a RFelectrode connected to the cover to face the substrate supported by thestage. Also, the RF electrode is connected to the RF power source.

In some exemplary embodiments of the present invention, the cover mayinclude a ceiling portion disposed over the stage and a protrudingportion extending downwardly from an edge of the ceiling portion anddisposed on the peripheral region of the stage. The protruding portionmay be ring-shaped, and the RF electrode may be disk-shaped and bedisposed on a lower surface of the ceiling portion.

In some exemplary embodiments of the present invention, the gas inletport may be defined by an inner surface of the protruding portion and anouter surface of the RF electrode. The RF electrode may have channelsconnected to the gas inlet port for supplying the source gas and theoxidizing gas. Each of the channels may widen towards the outer surfaceof the radio frequency electrode.

In some exemplary embodiments of the present invention, the chamber mayhave an outlet port disposed opposite the gas inlet port. An exhaustermay be connected to the outlet port for exhausting the source gas, theoxidizing gas and by-products of the oxidation reaction.

In some exemplary embodiments of the present invention, the apparatusmay further include a driving section for rotating the stage so as torotate the substrate supported by the stage.

In accordance with the exemplary embodiments of the present invention,the oxidation reaction between the metal precursor layer formed on thesubstrate and the oxidizing gas may be accelerated by applying the RFpower. The acceleration of the oxidation reaction may improve electricalcharacteristics and uniformity of the metal oxide on the substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the present invention will become readilyapparent along with the following detailed description when consideredin conjunction with the accompanying drawings.

FIG. 1 is a schematic view illustrating an apparatus for forming metaloxide in accordance with an exemplary embodiment of the presentinvention.

FIG. 2 is an enlarged cross-sectional view illustrating a gas inlet portin FIG. 1.

FIG. 3 is an enlarged cross-sectional view illustrating an outlet portin FIG. 1.

FIG. 4 is a schematic view illustrating a gas supply section in FIG. 1.

FIG. 5 is an enlarged cross-sectional view illustrating a RF electrodein FIG. 1.

FIG. 6 is a plan view illustrating the RF electrode in FIG. 1.

FIG. 7 is a flow chart illustrating a method of forming metal oxide on asubstrate using the apparatus in FIG. 1.

FIGS. 8 and 9 are graphs showing leakage current characteristics ofmetal oxide layers formed by a conventional method of forming metaloxide.

FIG. 10 is a graph showing leakage current characteristics of a metaloxide layer formed by a method of forming metal oxide in accordance withan exemplary embodiment of the present invention.

FIG. 11 is a graph showing leakage current characteristics of hafniumoxide layers formed by a conventional method of forming metal oxide anda hafnium oxide layer formed by a method of forming metal oxide inaccordance with an exemplary embodiment of the present invention.

FIG. 12 is a graph showing leakage current characteristics of hafniumoxide layers formed by methods of forming metal oxide in accordance withexemplary embodiments of the present invention.

FIG. 13 is a graph showing leakage current characteristics of azirconium oxide layer formed by a method of forming metal oxide inaccordance with an exemplary embodiment of the present invention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Embodiments of the invention now will be described more fullyhereinafter with reference to the accompanying drawings, in whichexemplary embodiments of the invention are shown. This invention may,however, be embodied in many different forms and should not be construedas limited to the embodiments set forth herein. Like reference numeralsrefer to like elements throughout. It will be understood that when anelement is referred to as being “on” another element, it can be directlyon the other element or intervening elements may be present.

FIG. 1 is a schematic view illustrating an apparatus for forming metaloxide in accordance with an exemplary embodiment of the presentinvention.

Referring to FIG. 1, an apparatus for forming metal oxide 100 may beused for forming metal oxide having a high dielectric constant on asemiconductor substrate 10 such as a silicon wafer. Particularly, theapparatus may be used for forming metal oxide such as hafnium oxide(HfO), zirconium oxide (ZrO), aluminum oxide (AlO), tantalum oxide(TaO), titanium oxide (TiO), lanthanum oxide (LaO), strontium oxide(SrO), barium oxide (BaO), praseodymium oxide (PrO), lead oxide (PbO),etc, on the semiconductor substrate 10. A layer including the metaloxide may be used as a gate insulating layer of a transistor, adielectric layer of a capacitor, and the like.

The semiconductor substrate 10 may be supported by a substrate stage200. The stage 200 may have a support region 210 for supporting thesemiconductor substrate 100 and a peripheral region 220 surrounding thesupport region 210. An upper surface of the peripheral region 220 may bedisposed higher than an upper surface of the support region 210. Forexample, the upper surface of the peripheral region 220 may have aheight substantially the same as that of an upper surface of thesemiconductor substrate 10 placed on the support region 210.

A heater 230 may be disposed in the stage 200 to heat the semiconductorsubstrate 10 to a predetermined process temperature. For example, themetal oxide may be formed at a temperature in a range of roomtemperature to about 450° C. Alternatively, a heating block for heatingthe semiconductor substrate 10 may be coupled to a lower portion of thestage 200.

A process chamber 300 may be disposed on the peripheral region 220 todefine a space in which the semiconductor substrate 10 is placed. Theprocess chamber 300 may include a cover 310 and a RF electrode 350.

The cover 310 may include a ceiling portion 320 and a protruding portion330. The ceiling portion 320 may be disk-shaped and disposed over thestage 200. The protruding portion 330 may extend downwardly from an edgeof the ceiling portion 320 and may have a ring shape. Further, theprotruding portion 330 is disposed on the peripheral region 220 of thestage 200. The RF electrode 350 may be disposed on a lower surface ofthe ceiling portion 320 to face the semiconductor substrate 10 placed onthe support region 210 of the stage 200. For example, the RF electrode350 may be coupled to the lower surface of the ceiling portion 320 by aplurality of fasteners.

FIG. 2 is an enlarged cross-sectional view illustrating a gas inletport, and FIG. 3 is an enlarged cross-sectional view illustrating anoutlet port.

Referring to FIGS. 2 and 3, the process chamber 300 may have a gas inletport 302, which supplies a source gas including metal precursor and anoxidizing gas including ozone, and an outlet port 304, which exhauststhe gases and by-produces of an oxidation reaction using the oxidizinggas.

The gas inlet port 302 may be adjacent to a first edge portion of thesemiconductor substrate 10, and the outlet port 304 may be adjacent to asecond edge portion opposite to the first edge portion of thesemiconductor substrate 10.

The gas inlet port 302 may be defined by a first inner surface 332 ofthe protruding portion 330 and a first outer surface 352 of the RFelectrode 350. The outlet port 304 may be defined by a second innersurface 334 of the protruding portion 330 and a second outer surface 354of the RF electrode 350. The first and second inner surfaces 332 and 334of the protruding portion 330 may be disposed to face with each other,and the first and second outer surfaces 352 and 354 may be disposed onopposite sides of the RF electrodes 350.

The source gas may flow along the upper surface of the semiconductorsubstrate 10 from the gas inlet port 302 towards the outlet port 304.Thus, a metal precursor layer may be formed on the semiconductorsubstrate 10. The oxidizing gas may flow along an upper surface of themetal precursor layer from the gas inlet port 302 towards the outletport 304, to thereby oxidize the metal precursor layer. Thus, metaloxide may be formed on the semiconductor substrate 10 by an oxidationreaction between the metal precursor layer and the oxidizing gas,thereby forming a metal oxide layer on the semiconductor substrate 10.That is, the source gas and the oxidizing gas may be supplied from thefirst edge portion towards the second edge portion of the semiconductorsubstrate 10.

Referring again to FIG. 1, a gas supply section 400 for supplying thesource gas and the oxidizing gas may be connected to the ceiling portion320 of the process chamber 300 by gas supply pipes. The source gas, theoxidizing gas and by-products formed while forming the metal oxide maybe exhausted by an exhauster 500 that is connected to the ceiling port320 of the process chamber 300 by an exhaust pipe.

FIG. 4 is a schematic view illustrating the gas supply section 400.

Referring to FIG. 4, the gas supply section 400 may include a first gassupply section 410 for supplying the source gas and a second gas supplysection 420 for supplying the oxidizing gas.

Examples of the first gas supply section 410 may include a liquiddelivery system (LDS), a bubbler including a bubbling container, and thelike.

Examples of metal that may be used for the source gas may includezirconium (Zr), hafnium (Hf), aluminum (Al), tantalum (Ta), titanium(Ti), lanthanum (La), strontium (Sr), Barium (Ba), praseodymium (Pr),lead (Pb), and the like. These can be used alone or in a combinationthereof. The source gas may be supplied along with a carrier gas intothe process chamber 300. Example of the carrier gas may include an inertgas such as argon (Ar).

The second gas supply section 420 may include an ozone generator. Theozone generator may generate ozone using an oxygen gas. That is, theoxidizing gas may be a gas mixture of ozone and oxygen, and aconcentration of ozone in the oxidizing gas may be in range of about 100to about 1000 g/m³. Particularly, a concentration of ozone in theoxidizing gas may be in a range of about 100 to about 500 g/m³. Forexample, a concentration of ozone in the oxidizing gas may be about 200g/m³.

The gas supply section 400 may further include a third gas supplysection 430 for supplying an inert gas used as a purge gas. The inertgas may be used for adjusting an internal pressure of the processchamber 300. For example, an interior of the process chamber 300 may beprimarily purged by a purge gas after forming the metal precursor layer,and may be secondarily purged by a purge gas after forming the metaloxide. An internal pressure of the process chamber 300 may be maintainedat a pressure in a range of about 0.1 to about 10 Torr, and an inert gasmay be supplied into the process chamber 300 along with the sourceand/or the oxidizing gas to adjust the internal pressure of the processchamber 300.

The gas supply section 400 may further include a fourth gas supplysection 440 for supplying an oxygen gas into the pressure chamber 300after primarily purging the interior of the process chamber. The fourthgas supply section 440 is provided to form an oxygen atmosphere in theprocess chamber 300 before oxidizing the metal precursor layer using theoxidizing gas. Alternatively, the oxygen gas may be supplied by thesecond gas supply section 420 instead of the fourth gas supply section440.

The first, second, third and fourth gas supply sections 410, 420, 430and 440 may be connected to the process chamber 300 by a plurality ofpipes. A first main pipe 450 and a second main pipe 452 may be connectedto the process chamber 300. A first divergent pipe 460 may diverge fromthe first main pipe 450, and the first gas supply section 410 may beconnected to the first main pipe 450 by the first divergent pipe 460. Asecond divergent pipe 462 may diverge from the second main pipe 452, andthe second gas supply section 420 may be connected to the second mainpipe 452 by the second divergent pipe 462. A third divergent pipe 470and a fourth divergent pipe 472 may diverge from the first and secondmain pipes 450 and 452, respectively. The third gas supply section 430may be connected to the first and second main pipes 450 and 452 by thethird and fourth divergent pipes 470 and 472, respectively. A fourth gassupply section 440 may be connected to the second main pipe 452 by aconnecting pipe 480.

Mass flow controllers 475 and valves 476 may be disposed in the first,second, third and fourth divergent pipes 460, 462, 470 and 472 and theconnecting pipe 480 to adjust flow rates of the source gas, theoxidizing gas, the purge gas, the pressure adjusting gas and the oxygengas. To avoid unduly cluttering the figure, only those mass flowcontrollers and valves on first pipe 460 are indicated.

The configuration including the pipes, the mass flow controllers and thevalves may be varied. Thus, the spirit and scope of the presentinvention may be not limited by the connecting relations between thepipes, the mass flow controller and the valves.

Referring again to FIG. 1, the process chamber 300 and the stage 200 maybe received in an outer chamber 600. A first driving section 700 forrotating the stage 200 and a second driving section 800 for verticallymoving the stage 200 may be disposed beneath the outer chamber 600.

The first driving section 700 may rotate the stage 200 in a stepwisemanner. That is, the first driving section 700 may rotate the stage 200by a predetermined angle to improve thickness uniformity of the metaloxide layer while forming the metal oxide layer. For example, the firstdriving section 700 may rotate the stage 200 by a predetermined angle,for example, approximately 60°, 90°, 180°, etc, posterior to theformation of the metal precursor layer, the primarily purging step, theoxidation of the metal precursor layer and the secondarily purging step.Then, the steps for forming metal oxide may be repeatedly performed.That is, the steps for forming metal oxide and the rotation of the stage200 may be repeatedly performed several times, thereby improvingthickness uniformity of the metal oxide layer.

In accordance with another example embodiment, the semiconductorsubstrate 10 may be continuously rotated. The steps for forming themetal oxide may be repeatedly performed while continuously rotating thesemiconductor substrate 10.

Further, the first driving section 700 may only rotate the supportregion 210 of the stage 200 while repeatedly performing the steps forforming the metal oxide.

The second driving section 800 may move the stage 200 in a verticaldirection to load or unload the semiconductor substrate 10.

Although not shown in figures, a plurality of lift pins may be disposedin the outer chamber 600. Particularly, the lift pins may be movablydisposed in the vertical direction through the stage 200 to load orunload the semiconductor substrate 10. A gate valve (not shown) may bedisposed in a side wall of the outer chamber 600 to transfer thesemiconductor substrate 10.

The exhauster 500 may be connected to the process chamber 300 to exhaustthe source gas, the oxidizing gas and the by-products formed whileforming the metal oxide.

The exhauster 500 may include a high vacuum pump and a roughing pump.The interior of the process chamber 300 may be maintained at a pressurein a range of about 0.1 to about 10 Torr by the exhauster 500 whileforming the metal oxide.

FIG. 5 is an enlarged cross-sectional view illustrating the RF electrode350, and FIG. 6 is a plan view illustrating the RF electrode 350.

Referring to FIGS. 2, 3, 5 and 6, the ceiling portion 320 of the cover310 may have a first connecting port 322 connected to the first mainpipe 450 for supplying the source gas, a second connecting port 324connected to the second main pipe 452 for supplying the oxidizing gasand a third connecting port 326 for communication with the exhauster500.

A first channel 360 may be provided in an upper surface portion of theRF electrode 350. The first channel 360 may be in communication with thefirst connecting port 322 and may widen towards the first outer surface352 of the RF electrode 350. A second channel 362 may be provided underthe first channel 360 in the RF electrode 350. The second channel 362may be in communication with the second connecting port 324 through afourth connecting port 364 that is formed in the RF electrode 350, andmay widen towards the first outer surface 352 of the RF electrode 350.Further, a third channel 366 may be provided in the upper surfaceportion of the RF electrode 350. The third channel 366 may be incommunication with the third connecting port 326 and may widen towardsthe second outer surface 354 of the RF electrode 350. Each of the first,second and third channels 360, 362 and 366 may be fan-shaped as shown inFIG. 6.

As described above, because the first and second channels 360 and 362widen towards the first outer surface 352 of the RF electrode 350, thesource gas and the oxidizing gas may be uniformly supplied along thesurface of the semiconductor substrate 10 and the surface of the metalprecursor layer.

Referring again to FIG. 1, the RF electrode 350 may be connected to a RFpower source 900 to apply a RF power to the oxidizing gas flowing alongthe surface of the metal precursor layer. The RF power may be applied toaccelerate the oxidation reaction between the metal precursor layer andthe oxidizing gas. In case the RF power is applied to the oxidizing gas,the concentration of ozone in the oxidizing gas may be increased, and aconcentration of oxygen radical in the oxidizing gas may be alsoincreased. As a result, the oxidation reaction between the metalprecursor layer and the oxidizing gas may be accelerated.

FIG. 7 is a flow chart illustrating a method of forming metal oxide onthe semiconductor substrate 10 using the apparatus 100 as shown in FIG.1.

Referring to FIG. 7, in step S100, the semiconductor substrate 10 suchas a silicon wafer may be placed on the stage 200. Particularly, thesemiconductor substrate 10 may be transferred into an interior of theouter chamber 600 through the gate valve of the outer chamber 600 andmay be then loaded on the stage 200 by the lift pins. Then, the seconddriving section 800 moves the stage 200 upwards so as to place thesemiconductor substrate 10 in the process chamber 300.

Patterns having electrical characteristics may be formed on thesemiconductor substrate 10. For example, active patterns that areelectrically isolated by the field oxide layer may be formed on thesurface of the semiconductor substrate 10. Further, the semiconductorsubstrate 10 may have conductive structures that serve as lowerelectrodes of capacitors and have a cylindrical shape.

In step S200, a source gas including metal precursor may be suppliedinto the process chamber 300 to form a metal precursor layer on thesemiconductor substrate 10. Here, the source gas may be supplied to flowalong the surface of the semiconductor substrate 10 from the first gassupply section 410 through the first channel 360 and the gas inlet port302. Examples of metal that may be used for the metal precursor mayinclude zirconium (Zr), hafnium (Hf), aluminum (Al), tantalum (Ta),titanium (Ti), lanthanum (La), strontium (Sr), Barium (Ba), praseodymium(Pr), lead (Pb), and the like. Examples of a source gas includingzirconium (Zr) may include tetrakis ethyl methyl amino zirconium (TEMAZ;Zr[N(CH₃)(C₂H₅)]₄), zirconium tert-butoxide (Zr[OC(CH₃)₃]₄), which mayalso be referred to as Zr(O^(t)Bu)₄ or zirconium butyl oxide, and thelike. These may be used alone or in a combination thereof. Examples of asource gas including hafnium (Hf) may include tetrakis dimethyl aminohafnium (TDMAH; Hf[N(CH3)2]4), tetrakis ethyl methyl amino hafnium(TEMAH; Hf[N(C2H5)CH3]4), tetrakis diethyl amino hafnium (TDEAH;Hf[N(C2H5)2]4), hafnium tert-butoxide (Hf[OC(CH₃)₃]₄),Hf[OC(CH3)2CH2OCH3]4, and the like. These may be used alone or in acombination thereof.

The source gas may be formed by forming a liquid metal precursor into anaerosol mist using an atomizer and then vaporizing the aerosol mistusing a vaporizer. Alternatively, the source gas may be formed bybubbling of a carrier gas into a liquid metal precursor.

The metal precursor layer may be formed while the source gas flows alongthe surface of the semiconductor substrate 10. The metal precursor layermay be an atomic layer chemisorbed on the surface of the semiconductorsubstrate 10. Further, the metal precursor may be physisorbed on thechemisorbed metal precursor layer, so that a second layer including thephysisorbed metal precursor may be formed.

In step S300, a purge gas may be supplied into the interior of theprocess chamber 300. The purge gas may be supplied from the third gassupply section 430 into the process chamber 300 through the first andsecond channels 360 and 362 and the gas inlet port 302. The second layermay be removed from the chemisorbed metal precursor layer by the supplyof the purge gas and vacuum evacuation of process chamber 300. Further,the source gas remaining in the process chamber 300 may be also removedfrom the process chamber 300 along with the purge gas by the vacuumevacuation.

In step S400, an oxidizing gas including ozone may be supplied into theprocess chamber 300 to oxidize the metal precursor layer. The oxidizinggas may be supplied to flow along a surface of the metal precursor layerfrom the second gas supply section 420 through the second channel 362and the gas inlet port 302.

In step S500, a RF power may be applied to accelerate an oxidationreaction between the metal precursor layer and the oxidizing gas. The RFpower may be applied to the oxidizing gas flowing along the surface ofthe metal precursor layer by the RF electrode 350, which is connected tothe RF power source 900. A concentration of oxygen radical in theoxidizing gas may be increased by applying the RF power, and theoxidation reaction between the metal precursor layer and the oxidizinggas may be then accelerated.

As a result, a metal oxide layer having improved electricalcharacteristics may be formed on the semiconductor substrate 10.Particularly, in case cylindrical lower electrodes having a high aspectratio are formed on a semiconductor substrate, the method of formingmetal oxide in accordance with the embodiments of the present inventionmay be desirably employed.

Though sequentially performed in FIG. 7, the steps S400 and S500 may beperformed at the same time.

Further, step S350 may be performed prior to step S400. In step S350, anoxygen gas may be supplied into the process chamber 300 to remove thepurge gas from the process chamber 300 and to form an oxygen atmospherein the process chamber 300. For example, the oxygen gas may be suppliedfrom the fourth gas supply section 440 through the second channel 362and the gas inlet port 302 for about 0.1 to about 3 seconds.

In step S600, a purge gas may be supplied into the process chamber 300.The purge gas may be supplied from the third gas supply section 430through the first and second channels 360 and 362 and the gas inlet port302 into the process chamber 300. The oxidizing gas and by-productsremaining in the process chamber may be removed along with the purge gasfrom the process chamber 300 through the outlet port 304 and the thirdchannel 366.

While performing the steps S200 through S600, the semiconductorsubstrate 10 may be heated to a predetermined process temperature by theheater 230. For example, the semiconductor substrate 10 may bemaintained at a process temperature in a range of room temperature toabout 450° C. Further, the interior of the process chamber 300 may bemaintained at a pressure in a range of about 0.1 to about 10 Torr whileperforming the steps S200 through S600. For example, the interior of theprocess chamber 300 may be maintained at a pressure of about 3 Torr by apressure adjusting gas supplied from the third gas supply section 430and the operation of exhauster 500.

In step S700, the semiconductor substrate 10 may be rotated by apredetermined angle. For example, the semiconductor substrate 10 may berotated by the first driving section 700 by about 60°, 90°, 180°, etc.

In step S800, the steps S200 through S600 may be repeatedly performed.The steps S700 and S800 may be repeatedly performed to form a metaloxide layer having a desired thickness on the semiconductor substrate10. As a result, a metal oxide layer having improved electricalcharacteristics and thickness uniformity may be formed on thesemiconductor substrate 10.

In accordance with another example embodiment of the present invention,the semiconductor substrate 10 may be continuously rotated whilerepeatedly performing the steps S200 through S600 at a predeterminedspeed.

Experiments were performed to inspect electrical characteristics ofmetal oxide layers formed by conventional methods of forming metal oxideand methods of forming metal oxide in accordance with exampleembodiments of the present invention.

Comparative Example 1

A first hafnium oxide layer was formed on a semiconductor substratehaving cylindrical lower electrodes by a conventional PEALD processusing oxygen plasma. Particularly, a process temperature was maintainedat about 300° C., and a pressure in a process chamber was maintained atabout 3 Torr while forming the first hafnium oxide layer. Leakagecurrents through the first hafnium oxide layer were measured at a leftportion, a central portion and a right portion of the semiconductorsubstrate. Measured results were shown in FIG. 8.

Comparative Example 2

A second hafnium oxide layer was formed on a semiconductor substratehaving cylindrical lower electrodes by a convention ALD process using anoxidizing gas including ozone. Particularly, a process temperature wasmaintained at about 300° C., and a pressure in a process chamber wasmaintained at about 3 Torr while forming the second hafnium oxide layer.Leakage currents through the second hafnium oxide layer were measured ata left portion, a central portion and a right portion of thesemiconductor substrate. Measured results were shown in FIG. 9.

An equivalent oxide thickness (EOT) of a central portion of the firsthafnium oxide layer was approximately 20.1 Å. EOTs of a left portion anda right portion of the first hafnium oxide layer were approximately 19.1Å and approximately 19.6 Å, respectively.

An EOT of a central portion of the second hafnium oxide layer wasapproximately 29.8 Å. EOTs of a left portion and a right portion of thesecond hafnium oxide layer were approximately 28.7 Å and approximately28.6 Å, respectively.

Referring to FIGS. 8 and 9, leakage current characteristics of the firsthafnium oxide layer were poor in comparison with those of the secondhafnium oxide layer. However, distribution of leakage current of thesecond hafnium oxide layer was poor in comparison with that of the firsthafnium oxide layer.

Example 1

A third hafnium oxide layer was formed on a semiconductor substratehaving cylindrical lower electrodes by a method of forming metal oxidein accordance with an embodiment of the present invention.

An oxidizing gas having an ozone concentration of approximately 200 g/m³was used for forming the third hafnium oxide layer, and a RF power ofapproximately 250 W was applied by the RF electrode 350. Further, atemperature of the semiconductor substrate was maintained atapproximately 300° C., and a pressure in the process chamber 300 wasmaintained at approximately 3 Torr.

Leakage currents through the third hafnium oxide layer were measured ata left portion, a central portion and a right portion of thesemiconductor substrate. Measured results were shown in FIG. 10.

An EOT of a central portion of the third hafnium oxide layer wasapproximately 19.5 Å. EOTs of a left portion and a right portion of thethird hafnium oxide layer were approximately 20.1 Å and approximately19.5 Å, respectively.

Referring to FIG. 10, it is understood that the EOTs of the thirdhafnium oxide layer are similar to those of the first hafnium oxidelayer, and leakage current characteristics of the third hafnium oxidelayer are improved in comparison with those of the first hafnium oxidelayer.

It is difficult to directly compare the third hafnium oxide layer withthe second hafnium oxide layer, because the EOTs of the second hafniumoxide layer are thicker than those of the third hafnium oxide layer.However, it is understood that distribution of leakage current of thethird hafnium oxide layer is improved in comparison with that of thesecond hafnium oxide layer as shown in FIG. 10.

To directly compare the first, second and third hafnium oxide layers,variations of leakage current according to variations of electricalfield (applied voltage/EOT) were measured. Measured results were shownin FIG. 11.

Referring to FIG. 11, it is understood that the leakage currentcharacteristics of the third hafnium oxide layer are improved incomparison with those of the second hafnium oxide layer.

Example 2

A fourth hafnium oxide layer was formed on a semiconductor substratehaving cylindrical lower electrodes by a method of forming metal oxidein accordance with an embodiment of the present invention.

A RF power of approximately 100 W was applied by the RF electrode 350,and an oxidizing gas including ozone was supplied at a flow rate ofapproximately 100 sccm. Further, a temperature of the semiconductorsubstrate was maintained at approximately 300° C., and a pressure in theprocess chamber 300 was maintained at approximately 3 Torr.

Example 3

A fifth hafnium oxide layer was formed on a semiconductor substratehaving cylindrical lower electrodes by a method of forming metal oxidein accordance with still another embodiment of the present invention.

A RF power of approximately 100 W was applied by the RF electrode 350,and an oxidizing gas including ozone was supplied at a flow rate ofapproximately 500 sccm. Further, a temperature of the semiconductorsubstrate was maintained at approximately 300° C., and a pressure in theprocess chamber 300 was maintained at approximately 3 Torr.

Example 4

A sixth hafnium oxide layer was formed on a semiconductor substratehaving cylindrical lower electrodes by a method of forming metal oxidein accordance with still another embodiment of the present invention.

A RF power of approximately 250 W was applied by the RF electrode 350,and an oxidizing gas including ozone was supplied at a flow rate ofapproximately 100 sccm. Further, a temperature of the semiconductorsubstrate was maintained at approximately 300° C., and a pressure in theprocess chamber 300 was maintained at approximately 3 Torr.

Example 5

A seventh hafnium oxide layer was formed on a semiconductor substratehaving cylindrical lower electrodes by a method of forming metal oxidein accordance with still another embodiment of the present invention.

A RF power of approximately 250 W was applied by the RF electrode 350,and an oxidizing gas including ozone was supplied at a flow rate ofapproximately 500 sccm. Further, a temperature of the semiconductorsubstrate was maintained at approximately 300° C., and a pressure in theprocess chamber 300 was maintained at approximately 3 Torr.

Leakage currents through the fourth, fifth, sixth and seventh hafniumoxide layers were measured, and measured results were shown in FIG. 12.

EOTs of the fourth, fifth, sixth and seventh hafnium oxide layers wereapproximately 17.5 Å, approximately 16.0 Å, approximately 15.2 Å,approximately 15.9 Å, respectively. As shown in FIG. 12, it isunderstood that leakage current characteristics are improved as both theapplied RF power and the flow rate of the oxidizing gas are increased.

As a result, it is understood that a metal oxide layer having desiredleakage current characteristics may be formed by adjusting the RF powerin a range of about 100 to about 300 W and adjusting the flow rate in arange of about 100 to about 1000 sccm.

Example 6

A zirconium oxide layer was formed on a semiconductor substrate havingcylindrical lower electrodes which is formed in accordance with a designrule of about 70 nm by a method of forming metal oxide in accordancewith another embodiment of the present invention.

A RF power of approximately 250 W was applied by the RF electrode 350,and an oxidizing gas including ozone was supplied at a flow rate ofapproximately 500 sccm while forming the zirconium oxide layer. Further,a temperature of the semiconductor substrate was maintained atapproximately 300° C., and a pressure in the process chamber 300 wasmaintained at approximately 3 Torr.

Leakage currents through the zirconium oxide layer were measured at acentral portion, a left portion and a right portion of the semiconductorsubstrate, and measured results were shown in FIG. 13.

EOTs at the central, left and right portions of the zirconium oxidelayer were approximately 8.4 Å, approximately 8.4 Å and approximately7.9 Å, respectively. As shown in FIG. 13, it is understood that leakagecurrent characteristics and distribution of leakage current are improvedwhen the applied voltage is in a range of about ±1V.

In accordance with exemplary embodiments of the present invention, anoxidation reaction between a metal precursor layer on a semiconductorsubstrate and an oxidizing gas may be accelerated by applying a RF powerto the oxidizing gas. As a result, a metal oxide layer formed by theaccelerated oxidation reaction may have improved electricalcharacteristics and thickness uniformity.

Although exemplary embodiments of the present invention have beendescribed, it is understood that other embodiments of the presentinvention should not be limited to these exemplary embodiments butvarious changes and modifications can be made by those skilled in theart within the spirit and scope as hereinafter claimed.

1. Apparatus for forming metal oxide comprising: a substrate stagehaving a support region for supporting a substrate and a peripheralregion surrounding the support region; a chamber disposed on theperipheral region to define a space in which the substrate is placed,the chamber having a gas inlet port for supplying a source gas includingmetal precursor to allow the source gas to flow along a surface of asubstrate so that a metal precursor layer is formed on the substrate andsupplying an oxidizing gas including ozone to allow the oxidizing gas toflow along a surface of the metal precursor layer to oxidize the metalprecursor layer so that metal oxide is formed on the substrate; and aradio frequency power source connected to the chamber for applying aradio frequency power to the oxidizing gas flowing along the surface ofthe metal precursor layer to accelerate a reaction between the metalprecursor layer and the oxidizing gas.
 2. The apparatus of claim 1,further comprising: a first gas supply section for supplying the sourcegas onto the substrate; and a second gas supply section for supplyingthe oxidizing gas onto the metal precursor layer.
 3. The apparatus ofclaim 2, wherein the second gas supply section comprises an ozonegenerator.
 4. The apparatus of claim 3, wherein a concentration of theozone in the oxidizing gas is in a range of about 100 g/m³ to about 1000g/m³.
 5. The apparatus of claim 2, further comprising a third gas supplysection for supplying an oxygen gas onto the metal precursor layerbefore supplying the oxidizing gas.
 6. The apparatus of claim 2, furthercomprising a fourth gas supply section for supplying a purge gas ontothe metal precursor layer and the metal oxide.
 7. The apparatus of claim1, wherein the chamber comprising: a cover disposed on the peripheralregion of the stage; and a radio frequency electrode connected to thecover to face the substrate supported by the stage.
 8. The apparatus ofclaim 7, wherein the cover comprising: a ceiling portion disposed overthe stage; and a protruding portion extending downwardly from theceiling portion and disposed on the peripheral region of the stage,wherein the protruding portion is ring-shaped.
 9. The apparatus of claim8, wherein the radio frequency electrode is disposed on a lower surfaceof the ceiling portion and is disk-shaped.
 10. The apparatus of claim 9,wherein the gas inlet port is defined by an inner surface of theprotruding portion and an outer surface of the radio frequencyelectrode, and the radio frequency electrode has channels connected tothe gas inlet port for supplying the source gas and the oxidizing gas.11. The apparatus of claim 10, wherein each of the channels widenstowards the outer surface of the radio frequency electrode.
 12. Theapparatus of claim 9, wherein the chamber has an outlet port disposedopposite the gas inlet port.
 13. The apparatus of claim 1, furthercomprising an exhauster connected to the chamber for exhausting thesource gas, the oxidizing gas and by-products of the reaction.
 14. Theapparatus of claim 1, further comprising a driving section for rotatingthe stage.
 15. Apparatus for forming metal oxide comprising: a chamberto define a space in which a substrate is placed, the chamber having agas inlet port for supplying a source gas including metal precursor toallow the source gas to flow along a surface of the substrate so that ametal precursor layer is formed on the substrate and supplying anoxidizing gas including ozone to allow the oxidizing gas to flow along asurface of the metal precursor layer to oxidize the metal precursorlayer so that metal oxide is formed on the substrate; a radio frequencypower source connected to the chamber for applying a radio frequencypower to the oxidizing gas flowing along the surface of the metalprecursor layer to accelerate a reaction between the metal precursorlayer and the oxidizing gas; and an exhauster connected to the chamberfor exhausting the source gas, the oxidizing gas and by-products of thereaction.